linux-kernel - Re: [PATCH v2 10/13] EDAC/altera: Skip the panic notifier if kdump is loaded

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Date:   Wed, 17 Aug 2022 19:09:26 -0300
From:   "Guilherme G. Piccoli" <gpiccoli@...lia.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     pmladek@...e.com, Dinh Nguyen <dinguyen@...nel.org>,
        Tony Luck <tony.luck@...el.com>, akpm@...ux-foundation.org,
        bhe@...hat.com, kexec@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-hyperv@...r.kernel.org,
        netdev@...r.kernel.org, x86@...nel.org, kernel-dev@...lia.com,
        kernel@...ccoli.net, halves@...onical.com, fabiomirmar@...il.com,
        alejandro.j.jimenez@...cle.com, andriy.shevchenko@...ux.intel.com,
        arnd@...db.de, corbet@....net, d.hatayama@...fujitsu.com,
        dave.hansen@...ux.intel.com, dyoung@...hat.com,
        feng.tang@...el.com, gregkh@...uxfoundation.org,
        mikelley@...rosoft.com, hidehiro.kawai.ez@...achi.com,
        jgross@...e.com, john.ogness@...utronix.de, keescook@...omium.org,
        luto@...nel.org, mhiramat@...nel.org, mingo@...hat.com,
        paulmck@...nel.org, peterz@...radead.org, rostedt@...dmis.org,
        senozhatsky@...omium.org, stern@...land.harvard.edu,
        tglx@...utronix.de, vgoyal@...hat.com, vkuznets@...hat.com,
        will@...nel.org, linux-edac@...r.kernel.org
Subject: Re: [PATCH v2 10/13] EDAC/altera: Skip the panic notifier if kdump is
 loaded

On 17/08/2022 19:00, Borislav Petkov wrote:
> On Wed, Aug 17, 2022 at 06:56:11PM -0300, Guilherme G. Piccoli wrote:
>> But do you agree that currently, in case of a kdump, that information
>> *is not collected*, with our without my patch?
> 
> If for some reason that panic notifier does not get run before kdump,
> then that's a bug and that driver should not use a panic notifier to log
> hw errors in the first place.
> 

Indeed, the notifiers don't run before kdump by default, in a conscious
decision of the kdump maintainers.

You might be right, in the sense that maybe the edac error handler
shouldn't run as a panic notifier. Let's see if Tony / Dinh can chime in
on that discussion - we could move it to run in the kexec event as well,
so it'd always run before a kdump, but maybe the risk it offers during
panic time is not worth.

Again - a matter of a trade-off, a good compromise must be agreed by all
parties (kdump maintainers are usually extremely afraid of taking risks
to not break kdump).

Cheers!